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The synthesis of silver doped nano-particulate titanium dioxide (Ag/TiO2) using a microemulsion method and an investigation of its photocatalytic activity for the degradation of Acid Red 27 in distilled water under UV-irradiation is reported. The prepared Ag/TiO2 is characterized using transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy. The size of the Ag nanoparticles is around 5–15 nm, with almost uniform distribution on the TiO2 particles. The efficiency of the photocatalytic process is evaluated to establish the optimum conditions, found to be at 2 wt% of Ag loading on TiO2, catalyst dosage of 400 mg L−1, and calcination temperature of 300°C. Complete decolorization of the dye solution on Ag/TiO2 was observed in 20 min of UV irradiation in the optimum conditions. [ABSTRACT FROM AUTHOR]

Titanium dioxide nanoparticles with different average diameter of particles (8, 18 and 27 nm) and different crystal structure (anatase and rutile) were used for degradation of C.I. Acid Red 88 (AR88) as a model compound. The degree of degradation of AR88 by TiO2 nanoparticles under irradiation of UV-light (254nm) with TiO2-UV100 (8 nm diameter and 100% anatase) is lower than TiO2-Merck (27 nm diameter and 95% anatase). TiO2-P25 with structure of anatase and rutile (80:20) combination shows higher photoactivity than other samples such as TiO2-UV100 and TiO2-Merck. Kinetics of removal of AR88 with all of nanosized-TiO2 particles is pseudo-first-order. The apparent reaction rate constant (kap) for removal of AR88 in the presence of different nanosized-TiO2 particles decreases with increasing of AR88 initial concentration. For TiO2-P25 and TiO2-UV100 a linear relation and for TiO2-Merck a nonlinear relation between kap and light intensity were obtained. [ABSTRACT FROM AUTHOR]

In this work, TiO2 nanoparticles in anatase phase was prepared by sol-gel low temperature method from titanium tetra-isopropoxide (TTIP) as titanium precursor in the presence of acetic acid (AcOH). The effects of synthesis parameters such as AcOH and water ratios, sol formation time, synthesis and calcination temperature on the photocatalytic activity of TiO2 nanoparticles were evaluated. The resulting nanoparticles were characterized by X-ray diffraction, UV-Vis reflectance spectroscopy, transmission electron microscopy and Brunauer-Emmett-Teller techniques. Photocatalytic activity of anatase TiO2 nanoparticles determined in the removal of C. I. Acid Red 27 (AR27) under UV light irradiation. Results indicate that with increasing AcOH/TTIP molar ratio from 1 to 10, sol formation time from 1 to 3 h and synthesis temperature from 0 to 25°C, increases crystallite size of synthesized nanoparticles. It was found that optimal conditions for low temperature preparation of anatase-type TiO2 nanoparticles with high photocatalytic activity were as follows: TTIP:AcOH:water molar ratio 1:1:200, sol formation time 1 h, synthesis temperature 0°C and calcination temperature 450°C. [ABSTRACT FROM AUTHOR]

In this study, to investigate the application of heterogeneous photocatalysis in the removal of organic contaminants from aqueous media a novel tubular continuous-flow photoreactor with supported TiO2-P25 on glass plates was designed and constructed. The photoreactor comprises six quartz tubes and a UV lamp which was placed in the center of the quartz tubes. 4-nitrophenol (4-NP) as a most refractory pollutant was chosen as a probe pollutant to examine the photoreactor efficiency for environmental cleaning applications. Results of experiments show that the removal efficiency of 4-NP in this photoreactor is a function of photoreactor length, gas and liquid flow rates and 4-NP initial concentration. Kinetics analysis indicates that degradation of 4-NP in continuous-mode can be modeled with the Langmuir-Hinshelwood (L-H) model (kL-H = 1.5 mg L-1 min-1, Kads = 0.11 mg-1 L). A design equation was obtained with a combination of L-H modified equation and tubular reactor design equation. This equation can be used for estimation of 4-NP concentration in different photoreactor lengths under various operational parameters. Mineralization study was followed through total organic carbon (TOC) analysis and measurement of nitrite and nitrate as final degradation products. [ABSTRACT FROM AUTHOR]